1. Field of the Invention
The invention relates to a piston pump for a vehicle brake system, having a housing section and a piston that is guided displaceably in the housing section, a receiving element for receiving an inlet valve, a sealing element adjoining the receiving element for sealing off the piston from the housing section, and a piston rod adjoining the sealing element.
2. Description of the Prior Art
The piston pumps for known vehicle brake systems, in particular anti-lock systems (ABS), serve to control the pressure in wheel brake cylinders. In the ABS, the piston pumps are intended for instance for returning brake fluid from one or more wheel brake cylinders to a master cylinder. Often, the ABS functions in combination with traction control (TC). Another known system, the electronic stability program (ESP), improves driving safety by a further increment compared to ABS and TC. While ABS and TC act in the longitudinal travel direction, ESP affects the transverse dynamics and in principle is therefore transverse traction control. For all these systems and for other systems for increasing driving safety, piston pumps are used.
Known piston pumps intended for vehicle brake systems comprise among other things a cylinder, which is embodied in a housing and in which a piston is received longitudinally movably. The piston drive is usually effected by an eccentric drive, in which the rotary motion of a shaft driven by a drive motor is converted to a translational motion of the piston. In the process, the piston rod is pressed with its face end against the outer circumference of the eccentric element of the eccentric drive by a prestressing element, for instance in the form of a helical spring. Thus in the final analysis, a reciprocating pumping motion of the piston can be attained.
Moreover, known piston pumps, to control the fluid inflow, have an inlet valve embodied as a seat valve; in the cylinder, between the inlet valve and the piston, a sealing element is also provided, which is guided longitudinally movably in the cylinder. The piston of known piston pumps is mounted with its face end, disposed inside the cylinder, on the sealing element, so that a reciprocating piston motion is transmitted directly to the sealing element. On the end of the sealing element toward the inlet valve, a valve seat of the inlet valve embodied as a seat valve is embodied, and for the fluid inflow, a bore extending through the sealing element is provided, which extends as far as the valve seat, so that fluid flows through the inlet valve that is open in the intake phase. The barrier body of the inlet valve embodied as a seat valve is pressed via a spring element against the valve seat embodied on the sealing element, and the barrier body, the spring element, and the end, embodied as a valve seat, of the sealing element are received in a receiving element in the form of an inlet valve cap. The inlet valve cap serves as a brace for the spring element and as a guide for the barrier body. Around the inlet valve cap, there is a prestressing element in the form of a helical spring, which presses against a bracing body embodied on the inlet valve cap that is received in a recess embodied in the sealing element, in order to transmit the spring force, transmitted to the bracing body, to the piston mounted on the sealing element by way of the sealing element. In this way, prestressing can in the final analysis be transmitted to the piston, in order to press the piston against the eccentric element of the eccentric drive.
Thus viewed overall, many pump components are disposed in the cylinder of known piston pumps. As a consequence, assembling and disassembling know piston pumps is comparatively complex. Moreover, because of the many pump components provided, known piston pumps cannot be manufactured especially economically.